The present invention relates generally to systems for the aseptic packaging of food products. More particularly, the present invention relates to an apparatus and method for providing sterilization zones in an aseptic packaging sterilization tunnel.
Sterilized packaging systems in which a sterile food product is placed and sealed in a container to preserve the product for later use are well known in the art. Methods of sterilizing incoming containers, filling the containers with pasteurized product, and sealing the containers in an aseptic tunnel are also known.
Packaged food products can generally be categorized as high acid products (Ph below 4.5) or low acid products (Ph of 4.5 and above). The high acid content of a high acid product helps to reduce bacteria growth in the product, thereby increasing the shelf life of the product. The low acid content of a low acid product, however, necessitates the use of more stringent packaging techniques, and often requires refrigeration of the product at the point of sale.
Several packaging techniques, including extended shelf life (ESL) and aseptic packaging, have been developed to increase the shelf life of low acid products. During ESL packaging, for example, the packaging material is commonly sanitized and filled with a product in a presterilized tunnel under xe2x80x9cultra-cleanxe2x80x9d conditions. By using such ESL packaging techniques, the shelf life of an ESL packaged product is commonly extended from about 10 to 15 days to about 90 days. Aseptic packaging techniques, however, which require that the packaging take place in a sterile environment, using presterilized containers, etc., are capable of providing a packaged product having an even longer shelf life of 150 days or more. In fact, with aseptic packaging, the shelf life limitation is often determined by the quality of the taste of the packaged product, rather than by a limitation caused by bacterial growth.
For the aseptic packaging of food products, an aseptic filler must, for example, use an FDA (Food and Drug Administration) approved sterilant, meet FDA quality control standards, use a sterile tunnel or clean room, and must aseptically treat all packaging material. The food product must also be processed using an xe2x80x9cUltra High Temperaturexe2x80x9d (UHT) pasteurization process to meet FDA aseptic standards. The packaging material must remain in a sterile environment during filling, closure, and sealing operations.
Many attempts have been made, albeit unsuccessfully, to aseptically fill containers, such as bottles or jars having small openings, at a high output processing speed. In addition, previous attempts for aseptically packaging a low acid product in plastic bottles or jars (e.g., formed of polyethylene terepthalate (PET) or high density polyethylene (HDPE)), at a high output processing speed, have also failed. Furthermore, the prior art has not been successful in providing a high output aseptic filler that complies with the stringent United States FDA standards for labeling a packaged product as xe2x80x9caseptic.xe2x80x9d In the following description of the present invention, the term xe2x80x9casepticxe2x80x9d denotes the United States FDA level of aseptic.
In order to overcome the above deficiencies, the present invention provides a method and apparatus for providing aseptically processed low acid products in a container having a small opening, such as a glass or plastic bottle or jar, at a high output processing speed.
Many features are incorporated into the aseptic processing apparatus of the present invention in order to meet the various FDA aseptic standards and the 3A Sanitary Standards and Accepted Practices.
The aseptic processing apparatus of the present invention uses a gas such as filtered air to maintain a positive pressure within a filler apparatus. The filler apparatus includes a sterilization tunnel that is pressurized to a level greater than atmospheric pressure using filtered sterile air. The filler apparatus includes three interfaces with the ambient environment, each of which eliminates the possibility of external contamination. The first interface is where containers first enter the sterilization tunnel through a bottle infeed and sterilization apparatus. In accordance with the present invention, there is always an outflow of aseptic sterilant (e.g., hydrogen peroxide) enriched sterile air from the first interface to prevent contaminants from entering the sterilization tunnel. The second interface with the sterilization tunnel is the path where incoming lid stock enters a lid sealing and heat sealing apparatus. To prevent contamination, the lid stock passes through a hydrogen peroxide bath that provides an aseptic barrier for any contaminants that enter the sterilization tunnel through the second interface. The third interface with the sterilization tunnel is at an exit opening of a discharge apparatus where sealed containers leave the sterilization tunnel. Positive sterile air pressure within the sterilization tunnel ensures that sterile air is continuously flowing out of the exit opening of the discharge apparatus, thereby preventing contaminants from entering the sterilization tunnel through this interface.
The aseptic processing apparatus includes a conveying apparatus for transporting the containers through a plurality of processing stations located within the sterilization tunnel. The entire conveying apparatus is enclosed within the sterilization tunnel, and is never is exposed to unsterile conditions.
A plurality of partitions and a plurality of hot sterile air supply sources (e.g., conduits) provide a plurality of sterile zones within the sterilization tunnel. The sterile zones provide a plurality of sterilant concentration levels withing the sterilization tunnel. Additionally, the sterile zones provide a plurality of gas flow rates within the sterilization tunnel.
The interior surface of a container such as a bottle or jar is much more difficult to aseptically sterilize than the interior surface of a cup. A cup generally has a large opening compared to its height, whereas a bottle or jar generally has a small opening compared to its height and its greatest width (e.g., the ratio of the opening diameter to the height of the container is less than 1.0). A sterilant can be introduced, activated, and removed in a cup much more rapidly than in a bottle or jar. The processing speed when using a bottle or jar is limited, in part, by the time required to aseptically sterilize the interior surface of the bottle or jar. The aseptic processing apparatus of the present invention overcomes the processing speed limitations associated with the use of containers such as bottles or jars.
A high output processing speed is achieved in the present invention by applying a hot atomized sterilant, such as hydrogen peroxide spray onto the interior surface of each container, and by subsequently activating and removing the sterilant in a plurality of drying stations using hot sterile air. For example hydrogen peroxide breaks down into water and oxygen, and thus oxidizes and kills bacteria within the container. To achieve aseptic sterilization, a minimum container temperature is developed and held for a predetermined period of time (e.g., 131xc2x0 F. for 5 seconds) after application of the sterilant. Hot sterile air is delivered at a high volume and a relatively low temperature to dry the container and to prevent the container (if formed of plastic) from being heated to its softening temperature. After container drying, the residual hydrogen peroxide in the container is below a predetermined level (e.g., about 0.5 PPM (parts per million)).
The present invention generally provides an apparatus comprising:
a sterilization tunnel for surrounding a plurality of containers with pressurized gas; and
a plurality of zones within a sterilization tunnel having different sterilant concentration levels.
Also provided is a method comprising:
providing a sterilization tunnel for surrounding a plurality of containers with pressurized gas;
introducing sterilant from a sterilant supply source into the sterilization tunnel;
providing a plurality of sterilant concentration zones within the sterilization tunnel;
introducing pressurized gas from at least one gas supply source into the sterilization tunnel; and
allowing the pressurized gas to escape the sterilization tunnel.
The invention further provides an apparatus comprising:
means for providing a plurality of containers in a sterilization tunnel;
means for providing a plurality of sterilant concentration zones within the sterilization tunnel; and
means for providing a plurality of gas flow rates within the sterilization tunnel.